Mast cells and basophils are multifunctional immune cells and have been implicated in the pathogenesis of asthma and other pulmonary diseases. Although they are derived from distinct lineages, they share a number of important features which justifies discussing them collectively. This review covers the cellular characteristics and biological properties of both cell types, including origin, maturation and differentiation, morphological and phenotypical properties, as well as their capacity to secrete preformed and newly generated mediators of inflammation. In addition, the mechanisms of cell activation and priming of mast cells and basophils will be outlined, as well as the putative mechanisms through which both cell types communicate with other inflammatory cells. The final section of the review focuses on the possible pathogenetic role of mast cells and basophils in several pulmonary diseases, such as parasitic infections, allergic diseases, pulmonary fibrosis and malignant disorders.